High-speed camera snapshots may have pinpointed a spot in the brain that serves as a marker for depression. Investigators have observed that electrical chatter in the dentate gyrus—a C-shaped region of the hippocampus—contracts in depressed rats but expands again after the animals receive antidepressants.

The region may represent a common pathway or intersection for brain activity in those suffering from depression, offering a springboard from which to map that activity and better understand the condition, says Karl Deisseroth, a Stanford University neuroengineer and psychiatrist, who led the study published online this week by Science.

Finding a common depression pathway in humans that could guide the search for treatments remains a "holy grail" of psychiatry, he says. "One of the mysteries of depression is how there can be so many different causes … and so many different treatments." A common pathway would bridge them, he adds.

The researchers induced depressionlike symptoms in rats by blasting static noise or otherwise annoying the animals at unpredictable intervals for several weeks. The chronically stressed rats swam less vigorously in a tank of water, indicating their feelings of rodent hopelessness.

To analyze the rats' brains, the team extracted brain slices from depressed and normal animals, soaked them in voltage-sensitive dye, and prodded them with electrodes next to a high-speed camera. When the brain cells fired, they activated the dye.

The camera was trained on the hippocampus, a small peanut-shaped part of the brain known to play a role in learning and memory, including navigation, but also implicated in mood and depression. The team found a smaller aura of activity originating from the curved dentate gyrus than in normal rats [see image below].

"We can do the equivalent of looking at one circuit board in a computer and find something that predicts behavior," Deisseroth says.

The result fit with prior research indicating that accelerated growth of new brain cells in the dentate gyrus, in a process called neurogenesis, is necessary for antidepressants to cure rats of their depression. When fed fluoxetine (Prozac), the depressed rats experienced more rapid neurogenesis and the range of electrical signals from their dentate gyri spread as far as in normal rats, the group reports.

Matching up depressed behavior with hippocampal activity is "pretty amazing," says Helen Mayberg, professor of psychiatry and neurology at Emory University in Atlanta. "It tells us the hippocampus is very involved," she says, "but it doesn't tell us it's the origin of the problem."

The hippocampus sends and receives information to and from many other brain regions, and mapping those connections in depressed animals is the next step, she says.

The causes of depression remain elusive, but Deisseroth sees a connection between the disease and the way that damage to the hippocampus can prevent people from remembering where things are located.

Similarly, although depression sufferers may face the same obstacles as others, "they just can't seem to see a path forward," he says. With any luck, he adds, his group's finding will put researchers on a path to figuring out a way to help them.

3 Comments

1. 1. WardXmodem 02:59 AM 4/17/08

   I found it interesting that new brain cells grow under the influence of antidepressants.
   
   I have often wondered if long-undiagnosed depression would lead, like a learning process, to reinforcement of negative attitudes, responses, activities, etc.
   
   For example, as one of these, I seldom bothered to learn people's names, nor to say them when meeting them, and of course chose not to have many friends.
   
   Once on antidepressants, these "pathways" are so burned in, it seems "normal" to NOT learn names, NOT to greet people by saying their names, etc.
   
   All this points to -- if true -- the importance of early diagnosis and treatment. (I think my first antidepressants started at about age 50-55)

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2. 2. karlchwe 03:13 PM 8/12/08

   I believe brain cells grow all the time. According to the article, antidepressants cause brain cells to grow in a particular part of the brain.
   
   As to the relationship between that and your habits in thoughts and actions, that is pretty tenuous. It is like saying that the size of my car is related to where I drive. There might be some relation, but it is depends on a lot of other things.
   
   Part of therapy for depression involves changing old habits of thought or behavior, and replacing them with different ones. That process may, and probably does, have some physical effect on the brain, but there may be no relationship with this particular discovery.
   
   It would be nice to have some kind of overall theory for depression. One consequence might be we could avoid the lengthy trial period some patients and psychiatrists have to undergo, trying one drug after another until they hit upon the right one or ones.

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3. 3. supporter 06:32 PM 9/5/08

   Many well-known therapists believe that ;biological and psychological
   factors both play a large and affective Role .
   
   Here - In this comment - I will try to Deal with the biological one ..
   
   Feelings of depression are caused by a chemical change that affects
   how the brain functions.
   
   A normally functioning brain is a giant messaging system that controls
   everything from your heartbeat, to walking, to your emotions. The
   brain is made up of billions of components with called "nerve cells"
   or "neurons" . These nerve cells send and receive messages from the
   rest of all your body, using brain chemicals "neurotransmitters" .
   
   These chemicals in the human brain are responsible for our emotional
   state. Depression happens when these chemical messages are not
   correctly send or received between brain cells, which affect the
   communication.
   
   (i. e., A telephone): If your telephone has a weak signal, you can't
   hear the person on the other end. so it is disabled or unclear
   
   It has been proposed that even the people who already suffering
   depression, have a way to treat it passed on the biological side, This
   way is the "Medications" .
   The main role of the "Medications" Is to fortify weak signals by
   raising the levels of certain neurotransmitters . which guarantee that
   the brain's messages are submitted loud and clear.
   
   &More information and Related Topics at My Blog!
   http://no4depression.blogspot.com/
   

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